Novel nanoemulsions comprising fatty acid and n-acyl derivatives of amino acid salt

ABSTRACT

The present invention relates to novel oil-in-water nanoemulsions. The oil phase contains oil selected from the group consisting of triglyceride oil and/or petrolatum as well as C8 to C18 fatty acid; and the aqueous phase contains specific N-acyl derivatives of amino acid salt as emulsifier.

FIELD OF THE INVENTION

The present invention relates to novel oil-in-water (o/w) nanoemulsions.The nanoemulsions contain (1) an internal oil phase having triglycerideoils and/or petrolatum and C₈ to C₁₈ fatty acid; and (2) an externalaqueous phase containing surfactants which are salts of N-acylderivatives of dicarboxylic amino acids (e.g., aspartic acid, glutamicacid), salts of N-acyl derivatives of monocarboxylic acids (e.g.,glycine, alanine), or mixtures of such derivatives of mono anddicarboxylic amino acids.

The invention is concerned with the provision of such triglyceride oilsand petrolatum (benefit agents delivered from nanoemulsion) in smalldroplets (e.g., 400 nanometers or less), which are more aestheticallypleasing than compositions in which benefit agents are delivered in theform of larger oil droplets. The nanoemulsions further provides highdeposition of the triglyceride oil and/or petrolatum when beingincorporated in personal cleansing compositions. Further, surprisingly,excellent lather performance of personal cleansing compositions is foundwhen these benefit agents are present in the form of droplets of 400nanometers or less. Typically, the triglyceride oil and petrolatumbenefit agents tend to depress lather speed and volume when in the formof droplets of a few microns.

N-acyl derivatives of both dicarboxylic and monocarboxylic amino acidsurfactants of the invention are exceptionally mild surfactants whichform the novel nanoemulsions, and which, when the nanoemulsions areincorporated into fully formulated personal liquid cleaners, do notinterrupt formation of micellar and/or lamellar structured liquids, nordo they suppress lather. Nanoemulsions using only N-acyl derivatives ofdicarboxylic amino acid surfactants as emulsifier are claimed in aco-pending application, where (1) petrolatum jelly yields much largerdroplet size than triglyceride oils do under the similar processingconditions, and requires multiple passes at a process pressure of 5,000psi to achieve a droplet size less than 200 nanometers, depending onspecific types of petrolatum jelly; and (2) the dicarboxylic amino acidbased surfactants that are in powder format of high purity are moreexpensive and difficult to handle. Applicants have now found that use offatty acid as co-emulsifier provides several unexpected advantages.First, it permits the use of less expensive, easier to handle N-acylderivatives of amino acid surfactants (both mono and dicarboxylic aminoacid surfactants) which are in liquid form and contain a high level ofinorganic salt. Also nanoemulsions of much smaller droplet size can beprepared more efficiently (e.g., lower process pressure and/or fewerpasses through a homogenizer). Further, using fatty acid co-emulsifierpermits formation of the small-volume average droplets of our invention(20 to 400 nm) using, as indicated, not just derivatives of dicarboxylicamino acid, but also derivatives of mono carboxylic amino acids. In theabsence of fatty acid emulsifier, the volume average of the droplets ofpetrolatum (using liquid salt of N-acyl derivatives of monocarboxylicamino acids as emulsifier) is well above 400 nanometers.

Specifically, the co-emulsifier (subject of the invention), allowspreparation of particularly smaller petrolatum droplets (e.g., 300 nmand below, preferably 250 nm and below, more preferably 200 nm andbelow) in an efficient manner and further permits use of liquid salts ofN-acyl derivatives of both di- and mono-carboxylic amino acids.

BACKGROUND OF THE INVENTION

Skin moisturizing oils (including triglyceride oils and petrolatumbenefit agents noted above) are often delivered from personal cleansingcompositions (e.g., shower gels, facial and hand cleansers designed tocleanse and moisturize skin) in the form of large oil drops (e.g., 50 to200 microns or greater).

U.S. Pat. Nos. 5,584,293 and 6,066,608, both to Glenn, Jr., for example,disclose a moisturizing liquid personal cleansing emulsion with at least10% lipophilic skin moisturizing agent droplets having a diameter ofgreater than 200 microns.

U.S. Pat. No. 8,772,212 to Restrepo et al. discloses an isotropiccleansing composition containing high level of petrolatum; greater than50% by volume of the petrolatum particles have a diameter greater than50, 100, 150 or 200 microns.

Compositions containing large oil drops need to be well structured sothey can suspend the large droplets (using, for example, stabilizers).U.S. Pat. Nos. 5,854,293 and 6,066,608, for example, utilize stabilizersselected from crystalline, hydroxyl-containing stabilizers, polymericthickeners, C10-C18 diesters, amorphous silica or smectite clay. Specialblending processes are typically needed to prepare such compositions.For example, compositions must be prepared under low shear to preventoil droplet size reduction (see U.S. Pat. No. 8,772,212). Although theyprovide enhanced delivery of benefit agents, these products aregenerally considered to be less aesthetically appealing to the consumerdue to the presence of large oil droplets.

Another method of enhancing the delivery of a benefit agent (e.g.,silicone) to the skin, for example, is through the use of cationichydrophilic polymers such as, for example,hydroxypropyltrimethylammonium derivative of guar gum, sold under thename JAGUAR® C-13-S (see U.S. Pat. No. 5,500,152 to Helliwell). In thisreference, silicone oil is a preformed emulsion with oil droplet sizeranging from 0.1-1 micron (μm), with a mean particle size of 0.4 μm(there is no mention whether this refers to number average or volumeaverage diameter of droplets). This kind of product tends to be smoothand aesthetically appealing. However, nourishing vegetable oils(triglyceride oils) and highly occlusive skin protectants, such aspetrolatum, are typically preferred moisturizers from a cleansingcomposition.

One challenge facing cleansing compositions that are rich inmoisturizing oils is that large amount of oils tend to depress thelather speed and volume.

It is therefore desirable to prepare a personal cleansing compositionconsisting of triglyceride oils and/or petrolatum nanoemulsion, which isaesthetically appealing, high in deposition of these moisturizing oils,and which maintains high lather performance.

In the subject invention, applicants provide novel nanoemulsions fordelivery of triglyceride oils and petrolatum as small (20 to 400nanometers, particularly 20 to 250, more particularly 20 to 200) volumeaverage diameter droplets. Further, unexpectedly, high latherperformance is maintained.

In a co-pending application, applicants claim similar nanoemulsionscomprising the salts of N-acyl derivatives of di-carboxylic amino acid(e.g., glutamic acid). In this application, using specificco-emulsifiers, unexpectedly applicants have found they can createnanoemulsions using liquid forms of both di- and mono-carboxylic aminoacid based surfactants. These high pH and high salt liquids are cheaperand easier to handle than the powder surfactants applicants werepreviously using, but are poor emulsifiers if not combined with fattyacid. Further, all other factors being equal, the co-emulsifier permitsformation of nanoemulsion with far smaller droplets, and/or using fewerhomogenizer passes or lower pressure. Even further, applicants havefound that they can form small droplet emulsions when using N-acylderivatives of mono-carboxylic amino acid as well (e.g., glycine).

Nanoemulsion of the invention comprise (1) an oil phase containingbenefit agent droplets selected from the group consisting oftriglyceride oils, petrolatum and mixtures thereof; and C₈ to C₁₈ fattyacid co-emulsifier and (2) an aqueous phase comprising one or moresurfactants (primary emulsifier) which are salts of N-acyl derivativesof dicarboxylic amino acid, salts of N-acyl derivatives ofmonocarboxylic acids or mixtures of such salts; specifically, thesesurfactants may be selected from (a) acylglutamate salt, acylaspartatesalt, acylglycinate salt, acylalaninate salt, with defined N-acylgroups, or (b) mixtures of any of these salts.

The specific N-acyl derivatives of amino acids (aspartic acid, glutamicacid, glycine and alanine) typically comprise 50% or greater, preferably60% or greater, more preferably 70% or greater of all surfactantspresent in the aqueous phase of the nanoemulson composition. The saltsof N-acyl derivatives of amino acid (any one alone or collectively) arepresent in an amount greater than any other surfactant present in theaqueous phase.

Both U.S. Pat. Nos. 8,834,903 and 6,541,018 to Simonnet et al. disclosenanoemulsion compositions in which acylglutamate is mentioned aspossible surfactant (e.g., U.S. Pat. No. 8,834,903 at column 4, lines27-31). However, it is disclosed as one of many possible surfactantsand, if used, the amino acid based surfactants are used as “additional”components, e.g., as co-surfactant (column 4, line 53). In the examples,the glutamate is never used at levels greater than 0.5% (10% by wt. oftotal surfactant). The exemplified glutamate is also a salt ofN-stearoyl-glutamic acid. This has C₁₈ chain length and provides poorlather in a cleansing application. There is no specific disclosure ofacylglutamate comprising 50% or more of surfactant in aqueous phase andfatty acid as co-emulsifier as in our invention.

In U.S. Pat. No. 6,541,018, the internal phase oils are primarily lowermolecular weight ester oils (MW less than 400). The lower MW ester oilimpacts viscosity and lather of cleansing compositions. Thetriglycerides of our invention and the petrolatum (having melting pointfrom 30° to 60° C.) of our invention help maintain good viscosity andfoam.

It is further noted that nanoemulsions disclosed in U.S. Pat. Nos.8,834,903 and 6,541,018 have an internal phase where concentration ofoil is no higher than 40% of the emulsion. While the concentration ofoils of the subject invention may range from 40% to 75% by wt. of totalnanoemulsion, preferred ranges are 41 to 70%, preferably 50% to 65%. Thehigher internal phase is beneficial not only because it consumes lessenergy to prepare nanoemulsions of smaller droplets, but it alsoimproves the yield of nano oil droplets.

It is also noted that, when the size of oil globules is defined in theSimonnet patents (see column 2, line 64 of U.S. Pat. No. 8,834,903), itis defined by number average. Since number average is the simpleaveraging of size of all particles (e.g., 1 μm droplet plus 99 μmdroplet average to about 50 μm) they do not account for volume averagediameter of droplet (e.g., volume average diameter of 1μ droplet and 99μdroplet is much closer to 99 μm). Thus, it is not clear that thesereferences disclose the same low volume average drops as disclosed inour invention.

US2003/0012759 A1 to Bowen-Leaver teaches preparation of nanoemulsionusing high pressure devices at about 10, 000 to 20, 000 psi and withmultiple passes ([0021] on page 3). It discloses an emulsifier systemconsisting of anionic surfactant (sodium stearoyl glutamate), non-ionicsurfactants (glyceryl stearate/PEG-100 stearate) and stearic acid inExample 1. Fatty acid is used with glyceryl stearate/PEG-100 stearate asco-emulsifiers in oil phase. There is no mention of criticality ofcombining acyl glutamate (anionic surfactant) and fatty acid asemulsifiers to improve production efficiency of nanoemulsion. In ourapplication, non-ionic emulsifiers, such as glyceryl stearate andPEG-100 stearate, are not included in the emulsifier system forpreparing nanoemulsions. The combination of acyl glutamate and fattyacid has been found to unexpectedly reduce petrolatum nanoemulsiondroplet size to below 200 nm after only one pass and at 5,000 psi orless, without any other non-ionic surfactants present. Such processefficiency, based on use of fatty acid, is completely unpredictable.

WO 02/080864 A1 discloses oil-in-water nanoemulsions comprising as itsprinciple emulsifiers a ternary system of surfactants comprising acationic, anionic and bridging surfactant (lines 16-17, page 2). Thenanoemulsion is prepared via a high pressure microfluidizer at 10,000 to20, 000 psi with at least two passes (lines 14-17, page 3)). Acylglutamate is one of the preferred anionic surfactants and fatty acid isoptionally included in the surfactant blend of six surfactants inexample 2 (lines 20˜21). No mention is made of specific advantages dueto addition of fatty acid. The oil level in the nanoemulsion is lessthan 30% while the oil level in our application is 40% and above.

US2003/0077299 A1 discloses an o/w nanoemulsion comprising an ionicsurfactant, a water phase and an oil phase which either comprises aceramide or fatty acid. N-acylglutamate salts are one of many examplesof anionic surfactants (lines 15˜17 in [0016] on page 1). In Example 1emulsion (6), nanoemulsion containing 16.4% silicone oil is prepared ata pressure of 2,800 kg/cm2 (˜40,000 psi) with three passes ([0060] onpage 4), using an emulsifier system consisting of fatty acids (palmiticacid and stearic acid) and acyglutamate. The oil level is far below40˜75%, the ratio of fatty acid/acyl glutamate(2) is much higher thanspecified in our application. The criticality of combing high oil level(e.g. 40% and above) and fatty acid/amino acid ratio is not appreciatedin reducing the processing energy in preparing nanoemulsions, especiallywhen petrolatum Jelly is concerned.

The unique nanoemulsions of the present invention contain small oildroplets (400 nanometers or less) which are aesthetically pleasing,efficiently deliver the benefit agent triglycerides oils or petrolatum,and maintain excellent lather when being incorporated into personalcleansing compositions. Further, the specific surfactants used,including the chain length of N-acyl chain, provide excellent, “mild”cleansing and ensure foam maintenance when the nanoemulsions are used inpersonal cleansing products.

With regard to mildness of surfactant, applicants note “Effect ofsurfactant mixtures on irritant contact dermatitis potential in man:sodium lauroyl glutamate and sodium lauryl sulphate” by C. H. Lee et al(Contact Dermatitis, Volume 30, Issue 4, pages 205-209, April 1994); andM. Sugar and R. Schmucker “Reduction of Skin's Surfactant Adsorption: AnEffective Way To Improve Mildness And Performance of Bath Care Products”(XXI IFSCC International Congress 2000, Berlin-Proceedings), wherein isdisclosed that sodium lauroyl glutamate and sodium cocyl glutamate, forexample, are mild surfactants and their utilization can decreaseirritation potential in sodium lauryl sulphate and SLES.

BRIEF DESCRIPTION OF THE INVENTION

Specifically, the present invention relates to nanoemulsion compositionscomprising:

-   -   a) an internal oil phase comprising (i) 40 to 75% by wt. of        total nanoemulsion of oil selected from the group consisting of        triglyceride oil, petrolatum and mixtures thereof, wherein the        melting point of the petrolatum is 30 to 60° C.; and (ii) 0.5 to        10% by wt. nanoemulsion of a C₈ to C₁₈, preferably C₁₀ to C₁₄        fatty acid (e.g., C₁₂ lauric acid), and    -   b) an external aqueous phase comprising 1.6 to 15% by wt. (as        active) of total nanoemulsion of a surfactant or surfactants        which are the salts of N-acyl derivatives of amino acid and,        preferably, said surfactant or surfactants is selected from the        group consisting of        -   (i) salt of N-acyl derivatives of di-carboxylic amino acid            (e.g., acylglutamate acid or acylaspartate), wherein greater            than 65% (e.g., 65 to 100%, preferably 65 to 90%) of the            acyl group has chain length of C₁₄ or less;        -   (ii) salt of N-acyl derivatives of mono-carboxylic acid            (e.g., acylglycinate, acylalanate), wherein greater than 65%            of the acyl group (e.g., 65 to 100%, preferably 65 to 90%)            has chain length C₁₄ or less; and        -   (iii) mixtures thereof;        -   wherein the surfactant of (b) comprises 50% or greater,            preferably 60% or greater, preferably 70% or greater,            preferably 75 to 100% of all surfactants present in the            aqueous phase of the nanoemulsion;        -   wherein the volume average diameter of the oil droplets            of (a) is 20 to 400 nanometers.

It should be understood that the claims are directed to the composition.That is, the claim is intended to cover the salts of N-acyl derivativesof amino acids, for example, whether formed by us or bought as aprepared surfactant product (as would occur in the vast majority of allcases).

Using fatty acid as co-emulsifier, nanoemulsions of the invention willtypically have volume average diameter of droplets of 350 or less, or 20to 300; or 20 to 250; or 20 to 200.

The nanoemulsions are typically prepared by mixing the oil phase and theaqueous phase using a conventional rotor/stator or other type of highshear devices and further processed via homogenizer at a processpressure of 7000 pounds per square inch (psi) or less, preferably 6000psi or less; most preferably 5000 psi or less. Using the samecomponents, but no C₈ to C₁₈ fatty acid as co-emulsifier in the oilphase, at the same pressure the droplet size will be typically higherthan if fatty acid is used.

Because greater than 65% of chain length of N-acyl chains on the aminoacid based surfactants are C₁₄ or less, the nanoemulsion composition,once formed, provides several advantages. For example, the nanoemulsioncomposition can be readily incorporated into personal cleanser liquidswhich are structured by micelles or are lamellar structured. Further,the predominantly shorter chain N-acyl groups (relative to longer chainC16 and C18, for example) on the surfactant enable good lather formationin the cleanser liquids.

Thus, the novel nanoemulsions are sensorially pleasing (due to smalldroplet size), provide efficient oil deposition, provide superiorstability (again because of smaller droplet size), and are ideallysuited (because of chain length selection) for use in personal cleansingliquids while providing excellent lather.

In another aspect, the invention relates to process for preparing anemulsion comprising:

-   -   a. an internal oil phase comprising (i) 40 to 75% by wt. of        total nanoemulsion of oil selected from the group consisting of        triglyceride oil, petrolatum and mixtures thereof, wherein the        melting point of the petrolatum is 30 to 60° C.; and (ii) 0.5 to        10% by wt. nanoemulsion of a C₈ to C₁₈, preferably C₁₀ to C₁₄        fatty acid (e.g., C₁₂ lauric acid), and    -   b. an external aqueous phase comprising 1.6 to 15% by wt. (as        active) of total nanoemulsion of a surfactant or surfactants        which are the salts of N-acyl derivatives of amino acid and,        preferably, said surfactant or surfactants is selected from the        group consisting of        -   i. salt of N-acyl derivatives of di-carboxylic amino acid            (e.g., acylglutamate acid or acylaspartate), wherein greater            than 65% (e.g., 65 to 100%, preferably 65 to 90%) of the            acyl group has chain length of C₁₄ or less;        -   ii. salt of N-acyl derivatives of mono-carboxylic acid            (e.g., acylglycinate, acylalanate), wherein greater than 65%            of the acyl group (e.g., 65 to 100%, preferably 65 to 90%)            has chain length C₁₄ or less; and        -   iii. mixtures thereof;        -   wherein the surfactant of (b) comprises 50% or greater,            preferably 60% or greater, preferably 70% or greater,            preferably 75 to 100% of all surfactants present in the            aqueous phase of the nanoemulsion;        -   wherein the volume average diameter of the oil droplets            of (a) is 20 to 400 nanometers        -   wherein said process comprises:            -   1) heating aqueous phase to 55 to 75° C.;            -   2) heating oil phase to 55 to 75° C. or until molten;            -   3) adding oil phase to aqueous phase and mixing to form                coarse emulsions in a rotor stator high shear device at                1000 to 6000 revolution per minute (rpm); or using a                homogenizer at pressure of 200 to 500 pounds per square                inch (psi);            -   4) pumping the coarse emulsion once or multiple times                through homogenizer at process pressure of 7000 psi or                less, preferably 6000 psi or less, preferably 5000 psi                or less; and            -   5) cooling emulsion to room temperature.

In step 3), alternatively, the coarse emulsion may be formed using ahomogenizer operating at pressure of 200 to 500 psi.

DETAILED DESCRIPTION OF THE INVENTION

Except in the examples, or where otherwise explicitly indicated, allnumbers in this description indicating amounts of material or conditionsof reaction, physical properties of materials and/or use are to beunderstood as modified by the word “about.” All amounts are by weight ofthe final composition, unless otherwise specified.

It should be noted that in specifying any range of concentration oramount, any particular upper concentration can be associated with anyparticular lower concentration or amount.

For the avoidance of doubt, the word “comprising” is intended to mean“including” but not necessarily “consisting of” or “composed of.” Inother words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered tocover all embodiments as found in the claims as being multiply dependentupon each other irrespective of the fact that claims may be foundwithout multiple dependency or redundancy.

The present invention provides novel nanoemulsions containing a specificselection of oils and surfactants. The nanoemulsions can be preparedusing processing pressure of 7000 psi or less. The novel nanoemulsionsare ideally suited for use in liquid cleansing compositions, forexample, structured (e.g., micellar or lamellar structured) liquidcleansing compositions.

Specifically, the N-acyl derivatives of amino acid surfactants (e.g.,acylglutamate, acylaspartate, acylglycinate, acylalanate surfactants)have greater than 65%, preferably greater than 75%, preferably greaterthan 80% of C₁₄ or less acyl chain (preferably they have greater than75% acyl chain which are C₁₂, C₁₄ and mixtures thereof). The chosensurfactants provide multiple advantages when final nanoemulsions aremixed into fully formulated liquid personal cleansing compositions.First, the amino acid surfactants are known to be less irritating thanharsher surfactants typically used such as sodium lauryl sulphate andsodium lauryl ether sulphate (SLES). Also, as noted, the chain length isselected so the surfactants are suitable for use in structured personalcleansing liquids while providing minimal interference with suchstructuring. Further, the selected predominantly shorter chain lengthsensure the surfactants will provide good foam.

In a co-pending application, applicants claim similar nanoemulsionswhich comprise N-acyl derivatives of di-carboxylic acids and which arenot specifically directed to those containing fatty acid emulsifier.Small size droplets are obtained. In this application, unexpectedly wehave found that using fatty acid as co-emulsifier yields significantlysmaller droplets, and these small droplet nanoemulsions are obtainedmore efficiently. Furthermore, using fatty acid as co-emulsifier permitsuse of N-acyl derivatives of amino acid surfactants which are in liquidformat, containing high amount of inorganic salts and with pH as high as10 (which were not used in co-pending cases). Surprisingly, theco-emulsifier permits production of small droplets whether the aminoacid surfactants are derivatives of dicarboxylic or mono-carboxylicamino acids. Small droplet size and efficient processing is function ofspecific combination of specific surfactants (e.g., anionic) andspecifically fatty acid. Higher amounts of fatty acid used withglutamate, for example, are more efficient (form smaller drops) thanusing more total surfactant, but lesser fatty acid. That is, a uniquesynergy between surfactants of the invention and fatty acid and, asnoted, works particularly well with oils (e.g. petrolatum jelly) of theinvention.

In short, significantly smaller droplets are obtained (using fattyacids) when using the same materials, and these small dropletnanoemulsions are obtained more efficiently. In general, small volumeaverage size droplets help provide more efficient deposition. Forexample, cationic polymers typically used in fully formulated liquidcleanser more readily deposit the smaller droplets than larger droplets.Large oil droplets also require stabilizers to suspend the large oildroplets. The small size oil droplets from the nanoemulsion, whenincorporated into a cleansing liquid, also provide greater stability.Small droplets are also viewed as more aesthetically pleasing.

The nanoemulsions of the invention are defined with more particularitybelow.

Oil Phase

Oils in the oil phase of the nanoemulsions may be triglyceride oil oroils (animal and/or vegetable oils); petrolatum; or mixtures of one ormore triglyceride oil with petrolatum. Petrolatum is particularlypreferred.

Examples of triglyceride oils which may be used include soybean oil,sunflower seed oil, coconut oil, rapeseed oil, palm oil, palm kerneloil, grape seed oil and fish oil. Soybean and sunflower seed oils arepreferred triglycerides.

The oil in the oil phase may also be petrolatum. The petrolatumpreferably has a melting point ranging from 30° to about 60° C. Examplesof such petrolatum oils include Vaseline® Petrolatum Jelly fromUnilever, White Petrolatum USP from Calumet Penreco, Petrolatum G2212and White Protopet® 1S from Sonneborn.

The oils can range from 40% to 75% by wt., preferably 41% to 65% by wt.of the total nanoemulsion composition. The preferred volume averagediameter of the triglyceride oil or petrolatum droplets is 20 to 400 nm,preferably 20 to 300 nm, more preferably 20 to 250 nm, or 20 to 200 nm.Lower level can be 20 or 30 or 40 or 50; upper level can be 300 or 250or 200 or 175 or 150.

The choice of triglyceride oils and petrolatum helps impart emolliencyand occlusivity to skin when the triglyceride oils and/or petrolatumdeposit onto skin after the skin is washed with fully formulatedcleansing compositions into which the nanoemulsions of this inventionhave been incorporated.

In addition to the triglyceride oil (or oils) and/or petrolatum, the oilphase may comprise oil soluble skin beneficial actives such as, forexample, Vitamin A, Vitamin E, sun screen, fragrances, retinolpalmitate, 12-hydroxy stearic acid, conjugated linoleic acid;antibacterial agents; mosquito repellents etc. at level of 0.01 to 5%.

Another ingredient which might be found in the oil phase is an oil phasestabilizer. For example, small amounts (0.01 to 2%, preferably 0.1-1% bywt. nanoemulsion) of antioxidant may be used. When the oil used istriglyceride, a preferred antioxidant which may be used is butylatedhydroxytoluene (BHT). This is often used as a food grade antioxidant.

In addition to oils, the oil phase contains C₈ to C₁₈, preferably C₁₀ toC₁₄ fatty acids in an amount ranging from 0.5 to 10% by wt. totalnanoemulsion. Examples of fatty acid which may be used include lauricacid, myristic acid, coconut fatty acid and mixtures thereof. The fattyacid is used as a co-emulsifier. For example, the oil phase may containpetrolatum ranging from 40 to 70% by wt, preferably 41 to 65% by wt. ofnanoemulsion and lauric acid ranging from 0.5 to 8% by wt. ofnanoemulsion.

Aqueous Phase

The aqueous phase contain salts of N-acyl derivatives of amino acids(e.g., di- or mono-carboxylic acid) as emulsifier (50% or greater,preferably 60% or greater of all surfactant present in the aqueousphase). Preferred di-carboxylic amino acid emulsifiers are acylglutamateand acylaspartate surfactants. Preferred mono-carboxylic amino acidemulsifiers are acylglycinate and acylalanate. Preferably, these arepotassium and/or sodium salts of N-acyl derivatives of amino acids,wherein greater than 65% of the acyl chains has chain length C₁₄ orless, e.g., C₈ to C₁₄ (e.g., derived from coconut fatty acid). The acylchains preferably have greater than 75%, more preferably greater than80% C₁₄ or less chain length. Preferably, greater than 75%, mostpreferably greater than 80% of the chain length are C₁₂, C₁₄ or mixturesthereof. These predominantly short chain acyl groups (relative to longerchain C16 and C18, for example) ensure that, when nanoemulsions of theinvention are incorporated into fully formulated liquid cleansingcompositions (especially structured liquid cleansing compositions), theyhelp maintain or enhance foaming capacity.

There are typically two formats of amino acid surfactants commerciallyavailable. One is powder or flake format, which is typically moreexpensive and high in purity. Examples of solid dicarboxylic amino acidsurfactants include:

-   -   sodium N-cocoyl-L-glutamate (e.g., Amisoft® CS-11 by Ajinomoto)    -   sodium N-lauroyl-L-glutamate (e.g., Amisoft® LS-11 by Ajinomoto)    -   sodium N-myristoyl-L-glutamate (Amisoft® MS-11 by Ajinomoto)    -   potassium N-cocoyl_I-Glutamate (e.g., Amisoft® CK-11 by        Ajinomoto)    -   potassium N-myristoyl-L-glutamate (Amisoft® MK-11 by Ajinomoto)    -   potassium N-lauroyl-L-glutamate (Amisoft® LK-11 by Ajinomoto)    -   Sodium Lauroyl Aspartate (AminoFoamer™ FLMS-P1 by Asahi Kasei        Chemical Corporation)    -   Sodium Lauroyl Glutamate (Aminosurfact™ ALMS-P1/S1 by Asahi        Kasei Chemical Corporation)    -   Sodium Myristoyl Glutamate (Aminosurfact™ AMMS-P1/S1 by Asahi        Kasei Chemical Corporation)

Examples of solid monocarboxylic amino acids surfactants include:

-   -   sodium cocoyl glycinate (e.g., Amilite® GCS-11 by Ajinomoto)    -   potassium cocoyl glycinate (e.g., Amilite® GCK-11 by Ajinomoto

One of unexpected discoveries of this invention is that, in addition toamino acids noted above (which are in powder form and are not convenientto handle in plant production), using fatty acid as co-emulsifierpermits use of amino acid surfactants in liquid form, which is typicallyless expensive but high in pH and inorganic salt As noted in thecomparative examples, in the absence of the fatty acid emulsifier,applicants could not form a coarse emulsion or droplet size was veryhigh (much greater than 400 nm); using acylglutamate, for example, thecoarse emulsion phase separated and/or, when using liquid acylglutamatewith high level of citric acid to lower the pH, droplet size was about2.5 times as large as when fatty acid is used. In the case ofacylglycinate, for example, without fatty acid the droplet size was 14times larger compared to when fatty acid was present. The addition of afatty acid, especially lauric acid, to the industrial liquid amino acidsurfactant as a co-emulsifier resulted in the formation of stable coarseemulsions and the efficient formation of smaller oil droplets to form ahighly superior nanoemulsion. For example, it was possible to producepetrolatum oil droplet sizes below 200 nm with only one pass through thehomogenizer at 5000 psi (see Example 6).

Liquid amino acid surfactants typically contain 20˜35% surfactantactive, high in pH and inorganic salt (e.g. from 3 to 6% NaCl). Examplesinclude:

-   -   AMISOFT® ECS-22SB: Disodium Cocoyl Glutamate (30% Aqueous        Solution)    -   AMISOFT® CS-22: Disodium Cocoyl Glutamate and sodium Cocoyl        Glutamate (25% Aqueous Solution)    -   AMISOFT® CK-22: Potassium Cocoyl Glutamate (30% Aqueous        Solution)    -   AMISOFT® LT-12: TEA-Lauroyl Glutamate (30% Aqueous Solution)    -   AMISOFT® CT-12 TEA-Cocoyl Glutamate (30% Aqueous Solution)    -   AMILITE® ACT-12: TEA-Cocoyl Alaninate (30% Aqueous Solution)    -   AMILITE® ACS-12: Sodium Cocoyl Alaninate (30% Aqueous Solution)    -   AMILITE® GCK-12/GCK-12K: Potassium Cocoyl Glycinate (30% Aqueous        Solution)    -   Aminosurfact™ ACDS-L: Sodium Cocoyl Glutamate (25% Aqueous        Solution)    -   Aminosurfact™ ACDP-L: Potassium Cocoyl Glutamate (22%)+Sodium        Cocoyl Glutamate (7%)    -   Aminosurfact™ ACMT-L: TEA-Cocoyl Glutamate (30% Aqueous        Solution)    -   AminoFoamer™ FLDS-L: Sodium Lauroyl Aspartate (25% Aqueous        Solution)

In addition to the Amisoft® and Amilite® series from Ajinomoto,Aminosurfact™ and AminoFoamer™ from Asahi Kasei Chemical Corporation,other suppliers of liquid amino acid surfactants include Clariant (e.g.Hostapon SG Sodium cocoyl glycinate), Solvay (e.g.Gerapon® PCG PotassiumCocoyl Glutamate aqueous solution; Gerapon® LG 3S sodium laurylglycinate with glycerin), Galaxy (Galsoft® KCGL Potassium CocoylGlutamate aqueous solution; GalSoft® SCG plus sodium cocoyl glycinate,20% active) and Sino Lion (Eversoft® USK-30K Potassium Cocoyl Glutamateaqueous solution; Eversoft® YCS-30S sodium cocoyl glycinate).

Additionally, other mild ionic cleansing surfactants can be used in theaqueous phase. Anionic surfactants which may be used include sodiumcocoyl isethionate, sodium cocoyl methyl isethionate, sodium lauroylisethionate, sodium methyl cocoyl taurate and other amino acid basedsurfactants, such as sodium lauroyl sarcosinate, sodium cocoylsarcosinate. Amphoterics such as coco betaine, cocamidopropyl betaine,sodium lauroamphoacetate, Lauramidopropyl hydroxysultaine andCocamidopropyl hydroxysultaine can also be used. These co-surfactantsare typically present at a level of less than 50%, preferably less than40%, more preferably less than 30% of total surfactants in the aqueousphase.

Overall surfactants in aqueous phase comprise 1.6 to 15% preferably 4 to12% by wt. of total nanoemulsion. As indicated, the salts of N-acylderivatives of amino acid, preferably acylglutamate, acylaspartate,acylglycinate, acylalaninate or mixtures thereof are the principalsurfactant of the nanoemulsion. They constitute 50% or greater,preferably 60% or greater of all surfactant in the aqueous phase.Preferably they constitute greater than 70%, more preferably greaterthan 75%. They may of course be the only surfactant present in theaqueous phase.

Preferably, the aqueous phase may contain a preservative orpreservatives. Typically, they are present at a level of 0.01 to 1.0%,preferably 0.1 to 0.5% by wt.

Nanoemulsions of the invention, have volume average diameter (also usedinterchangeably in and with terms “volume mean diameter” or “volumeaverage size”) of 400 nm or less, preferably 20 nm to 300 nm, morepreferably 20 to 250 nm, more preferably 20 to 200 nm.

Nanoemulsions with droplet sizes of these ranges are obtained in thesubject invention using relatively low pressure applied by a highpressure homogenizer or a high pressure sonolator. Pressures used are7000 psi or less, preferably 6000 psi or less, most preferably 5000 psior less.

Preparation of Nanoemulsion

Nanoemulsions are typically formed in a two-stage process.

The first mixing stage is used to form a coarse emulsion. The oil phaseand aqueous phase were heated up to 75° C. (55° to 75° C.) separatelysuch that each phase was clear and uniform (oil phase heated to 55 to75° C. or until molten); then the oil phase was mixed with the aqueousphase with intensive mixing. Intensive mixing can be accomplished viaconventional means including mixing the materials in a stirred tank andpassing the mixture through a rotor/stator mixer such as the Silverson®high shear in-line mixer or mixing them in the vessel with a high shearmixer such as the Scott® Turbon mixer. Alternatively, the coarseemulsion may be created by using a continuous high shear mixing devicesuch as the standard Sonolator device produced by Sonic Corporation ofConnecticut. These standard Sonolators are normally operated atpressures of 200-500 psi to form coarse emulsion.

The second stage of the process is to pass the coarse emulsion through ahigh pressure homogenizer to form the nano-emulsion. Suitable highpressure homogenizers are the Nano DeBee homogenizer of BEEInternational (Massachusetts, USA) and the High Pressure Sonolatordevice also produced by Sonic Corporation of Connecticut, USA. Thesedevices can be operated up to 1000-5000 psi in order to producenanoemulsions of less than 300 nm. For hydrophobic oils, eitherpetrolatum or triglycerides, only one pass through the Nano DeBEE orhigh pressure Sonolator is required to reach the desired nano-emulsionparticle size, when fatty acid is included as co-emulsifier.

In the examples, the following terms are defined as noted below:

-   -   Pass #: the number of times the emulsion passes through high        pressure homogenizer    -   D[4, 3]: volume average diameter or volume mean diameter or        volume average size    -   D[3, 2]: surface area mean diameter

The average diameters are determined by a Malvern Mastersizer.

Examples 1-6 and Comparatives A-H

Coarse emulsions were prepared in a one-liter ESCO mixer equipped with arotor/stator high shear device (ESCO-LABOR AG, Switzerland). The aqueousphase was added to the ESCO mixer and heated up to 75° C. or till clear.The oil phase was combined and heated up to 75° C. or till molten in aseparate container. The oil phase was gradually added to the aqueousphase in the ESCO mixer under agitation and/or was intensively mixed bythe rotor/stator device. When the addition of all oil phased wascompleted and the coarse emulsion was formed in the ESCO mixer, thecoarse emulsion was transferred and passed through High Pressurehomogenizer Nano DeBEE one or 2 times to arrive at the desired dropletsize at a process pressure of 5000 psi.

Examples 1-2 and Comparatives A-C

In Examples 1-2 and Comparatives A-C, liquid potassium cocoyl glutamate(27.2% active) high in pH (about 10) and high in inorganic salt (about 3to 6% KCl) was used as primary emulsifier. Coarse emulsions that arestable enough were passed through the Nano DeBEE once at a processpressure of 5000 psi to form nanoemulsions. The oil droplet size wasmeasured using Malvern Mastersizer afterwards.

Example Example Comparative Comparative Comparative 1 2 A B C IngredientWt. % Wt % Wt. % Wt. % Wt. % Oil Phase White petrolatum USP  50%  50% 50%  50%  50% Lauric acid   4%   2% Aqueous Phase Potassium Cocoyl27.4% 27.4% 27.4% 27.4% 27.4% Glutamate (Solvay, Active 27.2%) (7.5%active) (7.5% active) (7.5% active) (7.5% active) (7.5% active)Deionized Water Q.S.* Q.S.* Q.S.* Q.S.* Q.S.* Citric acid 1.28% 1.28%1.92% DMDM Hydantoin (and) 0.40%  0.4% 0.40% 0.40%  0.4% IodopropynylButylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000 5000  No coarse Coarse 5000  D_([3,2]) nm 127 138 emulsion emulsion 187D_([4,3]) nm 186 209 formed phase 476 separated in 2 minutes pH    6.76   5.71 10.0 5.57    5.22 *Amount needed (e.g., to obtain 100% by wt.)

No coarse emulsion was formed in comparative A. When 1.28% citric acidwas added to the aqueous phase as shown in Comparative B to lower the pHto the range about 5 to 6, coarse emulsion was formed with intensivemixing but phases quickly separated when the rotor/stator high sheardevice was stopped. When 1.92% citric acid was added to the aqueousphase as shown in Comparative C, coarse emulsion was formed and stayeduniform long enough to be passed through Nano DeBEE, yielding volumeaverage mean droplet size of 476 nm.

When 2 to 4% Lauric acid was added to the oil phase as shown in Example1 and 2, stable coarse emulsion formed with or without citric acid. Onepass through Nano DeBEE at the same process pressure of 5000 psi,yielding volume average mean droplet size as low as 186 nm. Thus,addition of lauric acid not only diminishes amount of citric acid neededto form coarse emulsion (Example 1), but formed much smaller droplets of209 or less in only one pass.

Example 3 and Comparative D

In Example 3 and Comparative D, liquid sodium cocoyl glycinate (20%active) high in pH (about 10) and high in inorganic salt (about 3 to 6%NaCl) was used as primary emulsifier. Coarse emulsions that are stableenough were passed via Nano DeBEE once at a process pressure of 5000 psiand the oil droplet size was measured using Malvern Mastersizerafterwards.

Comparative D Example 3 Ingredient Wt. % Wt % Oil Phase White petrolatumUSP 50% 50% Lauric acid  0%  4% Aqueous Phase Sodium Cocoyl Glycinate40% 40% (Galsoft, Active 20%) (8% active) (8% active) Deionized WaterQ.S. Q.S. DMDM Hydantoin (and) 0.40%  0.4%  IodopropynylButylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000 5000 D_([3,2]) nm 1900 161 D_([4,3]) nm 3917 266 pH    9.1    6.59

Although a coarse emulsion was formed when passing the compositionthrough Nano DeBEE at 5000 psi once, the oil droplet size was 3917 nm;when lauric acid was added to oil phase, under the same processconditions, oil droplets of 266 nm were obtained. Particle size was thus14 times smaller when using lauric acid than without using lauric acid.

Examples 4-5 and Comparatives E and F

The oil is soybean oil and the emulsifier is flake form of Potassiumcocoyl Glutamate (AMISOFT® CK-11). With or without lauric acid added tooil phase, stable coarse emulsions were formed and passed through NanoDeBEE once either at process pressure of 5000 psi or 3000 psi. The pH ofthe final nanoemulsions fall between about 5.6 to 5.8. At 5000 psi, with4% lauric acid added, the volume average droplet was reduced from 188 nmto 143 nm (see Comparative E and Example 4); at 3000 psi, with 4% lauricacid added, the volume average droplet was reduced from 268 nm to 161 nm(see Comparative F and Example 5).

Comparative Comparative Example Example E F 4 5 Ingredient Wt. % Wt %Wt. % Wt. % Oil Phase Soybean Oil  55%  55%  55%  55% BHT Food Grade0.4% 0.4% 0.4% 0.4% Antioxidant Lauric acid  4%  4% Aqueous PhasePotassium cocoyl 8.8% 8.8% 8.8% 8.8% Glutamate (AMISOFT ® CK-11)Deionized Water Q.S. Q.S. Q.S. Q.S. DMDM Hydantoin (and) Iodopropynyl0.40%  0.4% 0.40%  0.40%  Butylcarbamate(Glydant ™ Plus ™ Liquid)Process pressure, PSI 5000  3000  5000  3000  D_([3,2]) nm 127 163 113116 D_([4,3]) nm 188 268 143 161 pH    5.82    5.82    5.65    5.65

Example 6 and Comparatives G and H

Stable coarse emulsion was formed using 50% White Petrolatum andPotassium cocoyl Glutamate (AMISOFT® CK-11) as primary emulsifier withor without lauric acid as co-emulsifier. Without lauric acid, the coarseemulsion passed Nano DeBEE once and two times at 5000 psi separately,yielding nanoemulsion with volume average droplet of 374 nm and 283 nmrespectively. With 4% lauric acid and only one pass at 5000 psi throughNano DeBEE, the volume average droplet was reduced to 168 nm. Thus,lauric acid greatly improved the efficiency of small drop formation.

Compar- Compar- Example ative G ative H 6 Ingredient Wt. % Wt % Wt % OilPhase White Petrolatum USP  50% 50% 50%  Lauric acid 4% Aqueous PhasePotasium cocoyl Glutamate   8%  8% 8% (AMISOFT ® CK-11) Deionized WaterQ.S. Q.S. Q.S. DMDM Hydantoin (and) 0.40% 0.4%  0.4%  lodopropynylButylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000 5000  5000  Number of Passes  1  2  1 D_([3,2]) nm 188 168 120 D_([4,3])nm 374 283 168 pH    5.91    5.91    5.73

Examples 7-13: 50-55% Petrolatum was used to form nanoemulsions, withpotassium cocoyl glutamate (30%) or Sodium Cocoyl Glycinate (20%) in theliquid form as primary emulsifier, ranging 4 to 8.2% in active andlauric acid as co-emulsifier ranging 1 to 4%. The coarse emulsion wasprepared by a low pressure sonolator at a pressure up to 450 psi, wherethe molten oil phase and aqueous phase at 60 to 75 C were simultaneouslypumped through the orifice of a low pressure sonolator and thus formedthe coarse emulsion. The coarse emulsion was further pumped through ahigh pressure sonolator only once with a pressure up to 2500 psi to formnanoemulsion. Examples 12 and 13 used different lower pressure informing coarse emulsion and nanoemulsion as shown in the table.

With 4% lauric acid as co-emulsifier as shown in examples 10, 11 and 12,nanoemulsion with volume average droplet ranging from 144 to 198 nm wasformed after one pass of high pressure sonolator at pressure of 2500 psior less. With 4% lauric acid as co-emulsifier as shown in example 11 and12, even the coarse emulsion yielded volume average droplet size below300 nm after passing the low pressure sonolator at 450 psi or less.

Efficient production of small droplets is not believed to be justfunction of total surfactant amount, but rather of type and interactionof surfactants. This is seen comparing Example 7 to Example 10. Althoughthere is less overall surfactant active in Example 10 (8% vs. 9.2% inExample 7), because of interaction of anionic glutamate and greateramounts of fatty acid, the droplet size for petrolatum of Example 10 is158 nm versus 316 nm for Example 7.

Example 7 8 9 10 11 12 13 Ingredient Wt. % Wt % Wt. % Wt. % Wt. % Wt. %Wt. % Oil Phase Petrolatum G2212   55%   55%  55%  55% 55%   55% Whitepetrolatum 50% Lauric acid   1%   2%   2%   4%  4%   4%  4% AqueousPhase Potassium Cocoyl 27.3%  27.3%  13.3% 13.3% 20% 27.4% Glutamate(Galsoft KCGL, (8.2% (8.2% (4% (4% (6% (8.2% Active 30%)active) active) active) active) active) active) Sodium Cocoyl Glycinate40% (Galsoft SCG plus, (8% Active 20%) active) Deionized Water Q.S. Q.S.Q.S. Q.S. Q.S. Q.S. Q.S. DMDM Hydantoin 0.158%   0.158%   0.158% 0.158%  0.158%   0.158%   0.4%  (and) IodopropynylButylcarbamate(Glydant ™ Plus ™ Liquid) D_([4,3]), nm 855 514 560 350279 285 334 (coarse emulsion (350 (350 formed @450 psi) psi) psi)D_([4,3]), nm 316 217 286 158 144 198 228 (Nanoemulsion formed (10002000 @2500 psi) psi) psi) pH    8.4    7.88    7.36    7.0    7.23   7.25    6.7

1.-16. (canceled)
 17. A process for preparing an emulsion comprising: a)an internal phase comprising (1) 40 to 75% by wt. of a totalnanoemulsion composition of an oil phase containing benefit agentdroplets comprising oils selected from the group consisting oftriglyceride, petrolatum and mixtures thereof, wherein the melting pointof the petrolatum is 30 to 60° C.; and (ii) 0.5 to 10% by wt. of thetotal nanoemulsion composition of a co-emulsifier comprising C₈ to C₁₈fatty acid; and b) an external aqueous phase comprising 1.6 to 15% bywt. of the total nanoemulsion composition of a primary emulsifiercomprising a surfactant or surfactants which are the salts of N-acylderivatives of amino acid salt and wherein, said surfactant is selectedfrom the group consisting of; i. a salt of N-acyl derivatives ofdi-carboxylic amino acid wherein greater than 65% of the acyl group hasa chain length of C₁₄ or less; ii. a salt of N-acyl derivatives ofmono-carboxylic acid wherein greater than 65% of the acyl group has achain length C₁₄ or less; and iii. mixtures thereof; wherein thesurfactant of (b) comprises 50% or greater of all surfactants present inthe aqueous phase of the nanoemulsion; wherein a volume average diameterof the oil droplets of (a) is 20 to 400 nanometers wherein said processcomprises: 1) heating the external aqueous phase to 55 to 75° C.; 2)heating the internal oil phase to 55 to 75° C. or until molten; 3)adding the internal oil phase to the external aqueous phase and mixingto form coarse emulsions in a rotor stator high shear device at 1000 to6000 revolution per minute (rpm), or using a homogenizer at a pressureof 200 to 500 psi; 4) pumping the coarse emulsion once or multiple timesthrough the homogenizer at process pressure of 7000 psi or less; and 5)cooling the emulsion to room temperature.
 18. The process according toclaim 17, wherein in step 3), the coarse emulsion is formed using ahomogenizer operating at a pressure of 200 to 500 psi.
 19. The processaccording to claim 17, wherein the salt of N-acyl derivative ofdicarboxylic amino acid is a salt of acylglutamic acid, salt ofacylaspartic acid, or a mixture thereof.
 20. The process according toclaim 17, wherein the salt of N-acyl derivative of monocarboxylic aminoacid is a salt of acylgycine, salt of acylalanine, or a mixture thereof.21. The process according to claim 17, wherein the benefit agentdroplets are an oil, wherein the oil is a triglyceride oil and thetriglyceride oil is selected from the group consisting of soybean oil,sunflower seed oil, coconut oil, rapeseed oil, palm oil, palm kerneloil, grape seed oil, fish oil and mixtures thereof.
 22. The processaccording to claim 17, wherein the oil is petrolatum and the meltingpoint of the petrolatum is 30 to 60° C.
 23. The process according toclaim 17, wherein the oil is an oil mixture comprising triglyceride oiland petrolatum.
 24. The process according to claim 17, wherein the fattyacid having a chain length of C₈-C₁₈ is selected from the groupconsisting of lauric acid, myristic acid, coconut fatty acid andmixtures thereof.
 25. The process according to claim 17, wherein theco-emulsifier is a fatty acid present at a level of 1 to 7% by wt. 26.The process according to claim 17, wherein the salts of N-acylderivatives of the amino acid are mono- and/or di-sodium and/orpotassium salts.
 27. A nanoemulsion composition comprising: a) aninternal phase comprising (1) 40 to 75% by wt. of total nanoemulsioncomposition of an oil phase containing benefit agent droplets comprisingoils selected from the group consisting of triglyceride, petrolatum andmixtures thereof, wherein the melting point of the petrolatum is 30 to60° C.; and (ii) 1 to 10% by wt. nanoemulsion of a co-emulsifiercomprising a C₈ to C₁₈ fatty acid; and b) an external aqueous phasecomprising 1.6 to 15% by wt. of total nanoemulsion composition of aprimary emulsifier comprising a surfactant or surfactants which areN-acyl derivatives of amino acid salt; wherein the surfactant of (b)comprises 50% or greater of all surfactants present in said externalaqueous phase of the nanoemulsion; wherein the volume average diameterof droplets of (a) is 20 to 400 nanometers, wherein the salt of N-acylderivative of monocarboxylic amino acid is a salt of acylgycine, salt ofacylalanine, or a mixture thereof.
 28. The nanoemulsion compositionaccording to claim 27, wherein the surfactant or surfactants areselected from the group consisting of (i) salt of N-acyl derivatives ofdicarboxylic amino acid, wherein greater than 65% of the acyl group haschain length of C₁₄ or less; and (ii) salt of N-acyl derivatives ofmonocarboxylic amino acid, wherein greater than 65% of the acyl grouphas chain length C₁₄ or less; and (iii) mixtures thereof.
 29. Thenanoemulsion composition according to claim 27, wherein volume averagediameter of the droplets is 20 to 250 nm.
 30. The nanoemulsioncomposition according to claim 27, wherein the benefit agent dropletsare an oil, wherein the oil is a triglyceride oil and the triglycerideoil is selected from the group consisting of soybean oil, sunflower seedoil, coconut oil, rapeseed oil, palm oil, palm kernel oil, grape seedoil, fish oil and mixtures thereof.
 31. The nanoemulsion compositionaccording to claim 27, wherein the oil is petrolatum and the meltingpoint of the petrolatum is 30 to 60° C.
 32. The nanoemulsion compositionaccording to claim 27, wherein the oil is an oil mixture comprisingtriglyceride oil and petrolatum.
 33. The nanoemulsion compositionaccording to claim 27, wherein the fatty acid having a chain lengthC₈-C₁₈ is selected from the group consisting of lauric acid, myristicacid, coconut fatty acid and mixtures thereof.
 34. The nanoemulsioncomposition according to claim 27, wherein the co-emulsifier is a fattyacid present at a level of 1 to 7% by wt.
 35. The nanoemulsioncomposition according to claim 27, wherein the salts of N-acylderivatives of the amino acid are mono- and/or di-sodium and/orpotassium salts.
 36. The nanoemulsion composition according to claim 27,wherein the surfactant of (b), prior to formation of the nanoemulsion,is a powder or liquid surfactant.